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Listeria monocytogenes has shown the ability to grow on fresh uncut produce; however, the factors that control growth are not well understood. Peer-reviewed journal articles (n = 29) meeting the inclusion criteria and related to the growth of L. monocytogenes on fresh produce were found through university library databases and Google Scholar searches. Growth models were fit to each of the extracted 130 data sets to estimate log CFU per day rates of growth by using the DMFit tool. Multiple linear stepwise regression models for factors influencing growth rate were developed using R software. Factors included were temperature, nutrient level of inoculation buffer, initial cell concentration, final cell concentration, inoculation method, container permeability, and surface characteristics. The full model produced adjusted R2, Akaike information criterion, and root mean square error values of 0.41, 488, and 1.61, respectively. Stepwise regression resulted in a reduced model with parameters for incubation temperature, inoculation buffer type, initial and final cell concentrations, container characteristics, and produce surface characteristics. Model fit statistics improved slightly in the reduced model. A further reduced three-parameter model included storage temperature and initial and final cell concentrations, with interaction terms. This three-parameter model had adjusted R2, Akaike information criterion, and root mean square error values of 0.66, 417, and 1.24, respectively. Incubation temperature (P = 1.00E−09) initial cell concentration (P = 3.05E−12), and final cell concentration (P = 4.17E−09) all had highly significant effects on maximum growth rate. Our findings show the importance of inoculum concentration and produce microbial carrying capacity on the estimated growth rate and highlight the overall importance that temperature has on growth rate. Future experiments should consider initial inoculum concentration carefully when conducting growth studies for L. monocytogenes on whole produce. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes causes relatively few outbreaks linked to whole fresh produce but triggers recalls each year in the United States. There are limited data on the influence of wet versus dry inoculation methods on pathogen growth on whole produce. A cocktail of five L. monocytogenes strains that included clinical, food, and environmental isolates associated with foodborne outbreaks and recalls was used. Cultures were combined to target a final wet inoculum concentration of 4 to 5 log CFU/mL. The dry inoculum was prepared by mixing wet inoculum with 100 g of sterile sand and drying for 24 h. Produce investigated belonged to major commodity families: Ericaceae (blackberry, raspberry, and blueberry), Rutaceae (lemon and mandarin orange), Rosaceae (sweet cherry), Solanaceae (tomato), Brassaceae (cauliflower and broccoli), and Apiaceae (carrot). Whole intact, inoculated fruit and vegetable commodities were incubated at 2, 12, 22, and 35 ± 2°C. Commodities were sampled for up to 28 days, and the experiment was replicated six times. The average maximum growth increase was obtained by measuring the maximum absolute increase for each replicate within a specific commodity, temperature, and inoculation method. Data for each commodity, replicate, and temperature were used to create primary growth or survival models describing the lag phase and growth or shoulder and decline as a function of time. Use of a liquid inoculum (versus dry inoculum) resulted in a markedly increased L. monocytogenes growth rate and growth magnitude on whole produce surfaces. Temperature highly influenced this difference: a greater effect seen with more commodities at higher temperatures (22 and 35°C) versus lower temperatures (2 and 12°C). These findings need to be explored for other commodities and pathogens. The degree to which wet or dry inoculation techniques more realistically mimic contamination conditions throughout the supply chain (e.g., production, harvest, postharvest, transportation, or retail) should be investigated. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes was associated with more than 60 produce recalls, including tomato, cherry, broccoli, lemon, and lime, between 2017 and 2020. This study describes the effects of temperature, time, and food substrate as factors influencing L. monocytogenes behavior on whole intact raw fruits and vegetables. Ten intact whole fruit and vegetable commodities were chosen based on data gaps identified in a systematic literature review. Produce investigated belong to major commodity families: Ericaceae (blackberry, raspberry, and blueberry), Rutaceae (lemon and mandarin orange), Roseaceae (sweet cherry), Solanaceae (tomato), Brassaceae (cauliflower and broccoli), and Apiaceae (carrot). A cocktail of five L. monocytogenes strains that included clinical, food, or environmental isolates linked to foodborne outbreaks was used to inoculate intact whole fruits and vegetables. Samples were incubated at 2, 12, 22, 30, and 358C with relative humidities matched to typical real-world conditions. Foods were sampled (n ¼ 6) for up to 28 days, depending on temperature. Growth and decline rates were estimated using DMFit, an Excel add-in. Growth rates were compared with ComBase modeling predictions for L. monocytogenes. Almost every experiment showed initial growth, followed by subsequent decline. L. monocytogenes was able to grow on the whole intact surface of all produce tested, except for carrot. The 10 produce commodities supported growth of L. monocytogenes at 22 and 358C. Growth and survival at 2 and 128C varied by produce commodity. The standard deviation of the square root growth and decline rates showed significantly larger variability in both growth and decline rates within replicates as temperature increased. When L. monocytogenes growth occurred, it was conservatively modeled by ComBase Predictor, and growth was generally followed by decreases in concentration. This research will assist in understanding the risks of foodborne disease outbreaks and recalls associated with L. monocytogenes on fresh whole produce. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of foodborne pathogen diversity in preharvest environments is necessary to effectively track pathogens on farms and identify sources of produce contamination. As such, this study aimed to characterize Listeria diversity in wildlife feces and agricultural water collected from a New York state produce farm over a growing season. Water samples were collected from a pond (n¼80) and a stream (n¼52). Fecal samples (n¼77) were opportunistically collected from areas ,5 m from the water sources; all samples were collected from a ,0.5-km2 area. Overall, 86 (41%) and 50 (24%) of 209 samples were positive for Listeria monocytogenes and Listeria spp. (excluding L. monocytogenes), respectively. For each positive sample, one L. monocytogenes or Listeria spp. isolate was speciated by sequencing the sigB gene, thereby allowing for additional characterization based on the sigB allelic type. The 86 L. monocytogenes and 50 Listeria spp. isolates represented 8 and 23 different allelic types, respectively. A subset of L. monocytogenes isolates (n ¼ 44) from pond water and pond-adjacent feces (representing an ~5,000-m2 area) were further characterized by pulsed-field gel electrophoresis (PFGE); these 44 isolates represented 22 PFGE types, which is indicative of considerable diversity at a small spatial scale. Ten PFGE types were isolated more than once, suggesting persistence or reintroduction of PFGE types in this area. Given the small spatial scale, the prevalence of L. monocytogenes and Listeria spp., as well as the considerable diversity among isolates, suggests traceback investigations may be challenging. For example, traceback of finished product or processing facility contamination with specific subtypes to preharvest sources may require collection of large sample sets and characterization of a considerable number of isolates. Our data also support the adage “absence of evidence does not equal evidence of absence” as applies to L. monocytogenes traceback efforts at the preharvest level. [ABSTRACT FROM AUTHOR]

Past studies have shown that the on-farm distribution of Listeria monocytogenes is affected by environmental factors (e.g., weather). However, most studies were conducted at large scales (e.g., across farms), whereas few studies examined drivers of L. monocytogenes prevalence at smaller scales (e.g., within a single field). This study was performed to address this knowledge gap by (i) tracking L. monocytogenes distribution in two fields on one farm over a growing season and (ii) identifying factors associated with L. monocytogenes isolation from drag swab, soil, and agricultural water samples. Overall, L. monocytogenes was detected in 78% (21 of 27), 19% (7 of 36), and 8% (37 of 486) of water, drag swab, and soil samples, respectively. All isolates were characterized by pulsed-field gel electrophoresis. Of the 43 types identified, 14 were isolated on multiple sampling visits and/or from multiple sample types, indicating persistence in or repeated introduction into the farm environment during the study. Our findings also suggest that L. monocytogenes prevalence, even at the small spatial scale studied here, (i) was not uniform and (ii) varied more within fields than between fields or over time. This is illustrated by plot (in-field variation), field (between-field variation), and sampling visit (time), accounting for 18, 2, and 3% of variance in odds of isolating L. monocytogenes, respectively. Moreover, according to random forest analysis, water-related factors were among the top-ranked factors associated with L. monocytogenes isolation from all sample types. For example, the likelihood of isolating L. monocytogenes from drag and soil samples increased monotonically as rainfall increased. Overall, findings from this single-farm study suggests that mitigation strategies for L. monocytogenes in produce fields should focus on water-associated risk factors (e.g., rain and distance to water) and be tailored to specific high-risk in-field areas. [ABSTRACT FROM AUTHOR]

Understanding a food's ability to support the growth and/or survival of a pathogen throughout the supply chain is essential to minimizing large-scale contamination events. The purpose of this study was to examine the behavior (growth and/or survival) of Listeria monocytogenes on broccoli and cauliflower florets stored at different postharvest temperatures utilized along the supply chain. Broccoli and cauliflower samples were inoculated with L. monocytogenes at approximately 3 log CFU/g and stored at 23 ± 2, 12 ± 2, 4 ± 2, and −18 ± 2°C. Samples were evaluated for L. monocytogenes levels after 0, 0.167 (4 h), 1, 2, 3, and 4 days at 23 ± 2°C; 0, 0.167, 1, 2, 3, 4, 7, 10, and 14 days at 12 ± 2°C; 0, 0.167, 1, 2, 3, 4, 7, 10, 14, 21, and 28 days at 4 ± 2°C; and 0, 1, 7, 28, 56, 84, 112, 140, and 168 days at −18 ± 2°C. L. monocytogenes populations were determined by plating samples onto tryptic soy agar and modified Oxford agar supplemented with nalidixic acid. Broccoli and cauliflower supported the growth of L. monocytogenes at 23, 12, and 4°C, and higher growth rates were observed at higher temperatures. Populations of L. monocytogenes on broccoli and cauliflower samples significantly increased within 1 day at 23°C (by 1.6 and 2.0 log CFU/g, respectively) (P ≤ 0.05). At 12°C, populations of L. monocytogenes on broccoli and cauliflower samples significantly increased over 14 days by 1.4 and 1.9 log CFU/g, respectively (P ≤ 0.05). No significant difference over time was observed in L. monocytogenes populations on broccoli and cauliflower samples held under refrigeration until populations began to grow by day 10 in both commodities (P > 0.05). Under frozen storage (−18°C), populations of L. monocytogenes survived on broccoli and cauliflower at least up to 168 days. Storage of broccoli and cauliflower at lower temperatures can minimize L. monocytogenes growth potential; growth rates were lower at 4°C than at 12 and 23°C. Broccoli and cauliflower supported L. monocytogenes growth at 23, 12, and 4°C. L. monocytogenes survived up to at least 168 days on frozen broccoli and cauliflower. L. monocytogenes growth rates on both commodities were higher at 23°C than at 12 and 4°C. L. monocytogenes growth was not observed until day 10 on both commodities stored at 4°C. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes may be present in produce-associated environments (e.g., fields, packing houses); thus, understanding its growth and survival on intact, whole produce is of critical importance. The goal of this study was to identify and characterize published data on the growth and/or survival of L. monocytogenes on intact fruit and vegetable surfaces. Relevant studies were identified by searching seven electronic databases: AGRICOLA, CAB Abstracts, Center for Produce Safety funded research project final reports, FST Abstracts, Google Scholar, PubMed, and Web of Science. Searches were conducted using the following terms: Listeria monocytogenes, produce, growth, and survival. Search terms were also modified and “exploded” to find all related subheadings. Included studies had to be prospective, describe methodology (e.g., inoculation method), outline experimental parameters, and provide quantitative growth and/or survival data. Studies were not included if methods were unclear or inappropriate, or if produce was cut, processed, or otherwise treated. Of 3,459 identified citations, 88 were reviewed in full and 29 studies met the inclusion criteria. Included studies represented 21 commodities, with the majority of studies focusing on melons, leafy greens, berries, or sprouts. Synthesis of the reviewed studies suggests L. monocytogenes growth and survival on intact produce surfaces differ substantially by commodity. Parameters such as temperature and produce surface characteristics had a considerable effect on L. monocytogenes growth and survival dynamics. This review provides an inventory of the current data on L. monocytogenes growth and/or survival on intact produce surfaces. Identification of which intact produce commodities support L. monocytogenes growth and/or survival at various conditions observed along the supply chain will assist the industry in managing L. monocytogenes contamination risk. [ABSTRACT FROM AUTHOR]

Cucumbers were associated with four multistate outbreaks of Salmonella in the United States between 2013 and 2016. This study evaluated the fate of Listeria monocytogenes and Salmonella on whole and sliced cucumbers at various storage temperatures. Cucumbers were inoculated with five-strain cocktails of L. monocytogenes or Salmonella, air dried, and stored at 23 ± 2, 4 ± 2, and −18 ± 2°C. Whole and sliced cucumber samples were enumerated on nonselective and selective media at 0, 0.21, 1, 2, 3, and 4 days (23 ± 2°C); 0, 1, 2, 3, 7, 14, and 21 days (4 ± 2°C); and 0, 7, 28, 60, 90, and 120 days (−18 ± 2°C). For Salmonella, additional time points were added at 8 and 17 h (23 ± 2°C) and at 17 h (4 ± 2°C). Population levels were calculated for whole (CFU per cucumber) and sliced (CFU per gram) cucumbers. Both pathogens grew on whole and sliced cucumbers held at ambient temperatures. At 23 ± 2°C, L. monocytogenes and Salmonella populations significantly increased on whole (2.3 and 3.4 log CFU per cucumber, respectively) and sliced (1.7 and 3.2 log CFU/g, respectively) cucumbers within 1 day. Salmonella populations significantly increased on whole and sliced cucumbers after only 5 h (2.1 log CFU per cucumber and 1.5 log CFU/g, respectively), whereas L. monocytogenes populations were not significantly different on whole and sliced cucumbers at 5 h. L. monocytogenes and Salmonella populations survived up to 21 days on refrigerated whole and sliced cucumbers. At 4 ± 2°C, L. monocytogenes populations significantly increased on whole (2.8 log CFU per cucumber) and sliced (2.9 log CFU/g) cucumbers, whereas Salmonella populations significantly decreased on whole (0.6 log CFU per cucumber) and sliced (1.3 log CFU/g) cucumbers over 21 days. Both pathogens survived on frozen whole and sliced cucumbers for at least 120 days. The ability of L. monocytogenes and Salmonella to grow on whole and sliced cucumbers in short amounts of time at ambient temperatures, and to survive on whole and sliced cucumbers past the recommended shelf life at refrigeration temperatures, highlights the need to reduce the likelihood of contamination events throughout the cucumber supply chain. [ABSTRACT FROM AUTHOR]

Several produce-borne outbreaks have been associated with the use of contaminated water during preharvest applications. Salmonella has been implicated in a number of these outbreaks. The purpose of this study was to evaluate the microbial quality of agricultural surface water used in preharvest production on the Eastern Shore of Virginia in accordance with the Food Safety Modernization Act's Produce Safety Rule water standards. The study also examined the prevalence, concentration, and diversity of Salmonella in those water sources. Water samples (1 L) from 20 agricultural ponds were collected during the 2015 and 2016 growing seasons ( n = 400). Total aerobic bacteria, total coliforms, and Escherichia coli were enumerated for each sample. Population levels of each microorganism were calculated per 100-mL sample and log transformed, when necessary. Samples (250 mL) were also enriched for Salmonella. Presumptive Salmonella isolates were confirmed by PCR ( invA gene) and were serotyped. In 2016, the concentration of Salmonella in each sample was also estimated by most probable number (MPN). Indicator bacteria and environmental and meteorological factors were analyzed for their association with the detection of a Salmonella-positive water sample by using logistic regression analysis. Seventeen of the 20 ponds met the Food Safety Modernization Act's Produce Safety Rule standards for production agricultural water. Three ponds did not meet the standards because the statistical threshold value exceeded the limit. Salmonella was detected in 19% of water samples in each year (38 of 200 in 2015 and 38 of 200 in 2016). Of the 118 Salmonella isolates serotyped, 14 serotypes were identified with the most prevalent being Salmonella Newport. E. coli concentration, farm, and total aerobic bacteria concentration were significantly associated with the likelihood of detecting a Salmonella-positive sample The average concentration of Salmonella in all samples was 4.44 MPN/100 mL, with the limit of detection being 3.00 MPN/100 mL. The highest concentration of Salmonella was 93.0 MPN/100 mL. These data will assist in a better understanding of the risks that production water poses to produce contamination events. [ABSTRACT FROM AUTHOR]

In-shell pecan samples (500 g) were collected over four harvest seasons (2010 to 2014) from seven pecan shelling facilities located in five U.S. states. Four varieties of pecans were analyzed: Mexican Improved, Native Seedlings, Southern Improved, and Western Improved. Pecan samples (100 g) were sent to a third party laboratory for initial Salmonella screening. When a sample was positive for Salmonella, the pathogen level was determined by the most-probable-number (MPN) method (25, 2.5, and 0.25 g). Two sample preparation strategies were used for the MPN analysis, and both strategies were combined for the reported MPN values. Forty-four (0.95%) of 4,641 in-shell pecan samples were positive for Salmonella during initial screening; prevalence by year was 0.47 to 1.4%. Prevalence was not significantly different between varieties: Mexican Improved, 1.2%; Native/Seedling, 0.99%; Southern Improved, 0.97%; and Western Improved, 0.75%. Salmonella was not isolated from 31 of 44 samples upon retesting during MPN analysis (<0.47 MPN/100 g). When Salmonella was detected, the levels were 0.47 to 39 MPN/100 g, with a mean of 2.4 MPN/100 g. Thirty-one Salmonella serotypes were obtained from 42 Salmonella-positive pecan samples; Enteritidis was the most common (12% of samples) followed by Javiana (9%) and Braenderup (7%). All Salmonella Enteritidis isolates were phage type 8. Pulsed-field gel electrophoresis analysis (Xbal) revealed within-serotype diversity, indicating introduction of contamination from a variety of sources. Most (64%) of the isolates were resistant to streptomycin or tetracycline, and 13% were resistant to three or more antibiotics. Salmonella prevalence and level on in-shell pecans is comparable to that on other nuts. [ABSTRACT FROM AUTHOR]

Although flooding introduces microbiological, chemical, and physical hazards onto croplands, few data are available on the spatial extent, patterns, and development of contamination over time postflooding. To address this paucity of information, we conducted a spatially explicit study of Escherichia coli and Salmonella contamination prevalence and genetic diversity in produce fields after the catastrophic flooding that occurred in New England during 2011. Although no significant differences were detected between the two participating farms, both random forest and logistic regression revealed changes in the spatial pattern of E. coli contamination in drag swab samples over time. Analyses also indicated that E. coli detection was associated with changes in farm management to remediate the land after flooding. In particular, E. coli was widespread in drag swab samples at 21 days postflooding, but the spatial pattern changed by 238 days postflooding such that E. coli was then most prevalent in close proximity to surface water features. The combined results of several population genetics analyses indicated that over time postflooding E. coli populations on the farms (i) changed in composition and (ii) declined overall. Salmonella was primarily detected in surface water features, but some Salmonella strains were isolated from soil and drag swab samples at 21 and 44 days postflooding. Although postflood contamination and land management responses should always be evaluated in the context of each unique farm landscape, our results provide quantitative data on the general patterns of contamination after flooding and support the practice of establishing buffer zones between flood-contaminated cropland and harvestable crops in produce fields. [ABSTRACT FROM AUTHOR]

Environmental (i.e., meteorological and landscape) factors and management practices can affect the prevalence of foodborne pathogens in produce production environments. This study was conducted to determine the prevalence of Listeria monocytogenes, Listeria species (including L. monocytogenes), Salmonella, and Shiga toxin-producing Escherichia coli (STEC) in produce production environments and to identify environmental factors and management practices associated with their isolation. Ten produce farms in New York State were sampled during a 6-week period in 2010, and 124 georeferenced samples (80 terrestrial, 33 water, and 11 fecal) were collected. L. monocytogenes, Listeria spp., Salmonella, and STEC were detected in 16, 44, 4, and 5% of terrestrial samples, 30, 58, 12, and 3% of water samples, and 45, 45, 27, and 9% of fecal samples, respectively. Environmental factors and management practices were evaluated for their association with terrestrial samples positive for L. monocytogenes or other Listeria species by univariate logistic regression; analysis was not conducted for Salmonella or STEC because the number of samples positive for these pathogens was low. Although univariate analysis identified associations between isolation of L. monocytogenes or Listeria spp. from terrestrial samples and various water-related factors (e.g., proximity to wetlands and precipitation), multivariate analysis revealed that only irrigation within 3 days of sample collection was significantly associated with isolation of L. monocytogenes (odds ratio = 39) and Listeria spp. (odds ratio = 5) from terrestrial samples. These findings suggest that intervention at the irrigation level may reduce the risk of produce contamination. [ABSTRACT FROM AUTHOR]

Listeria species have been isolated from diverse environments, often at considerable prevalence, and are known to persist in food processing facilities. The presence of Listeria spp. has been suggested to be a marker for Listeria monocytogenes contamination. Therefore, a study was conducted to (i) determine the prevalence and diversity of Listeria spp. in produce production and natural environments and (ii) identify geographical and/or meteorological factors that affect the isolation of Listeria spp. in these environments. These data were also used to evaluate Listeria spp. as index organisms for L. monocytogenes in produce production environments. Environmental samples collected from produce production (n = 588) and natural (n = 734) environments in New York State were microbiologically analyzed to detect and isolate Listeria spp. The prevalence of Listeria spp. was approximately 33 and 34% for samples obtained from natural environments and produce production, respectively. Coisolation of L. monocytogenes and at least one other species of Listeria in a given sample was recorded for 3 and 9% of samples from natural environments and produce production, respectively. Soil moisture and proximity to water and pastures were highly associated with isolation of Listeria spp. in produce production environments, while elevation, study site, and proximity to pastures were highly associated with isolation of Listeria spp. in natural environments, as determined by randomForest models. These data show that Listeria spp. were prevalent in both agricultural and nonagricultural environments and that geographical and meteorological factors associated with isolation of Listeria spp. were considerably different between the two environments. [ABSTRACT FROM AUTHOR]

Abstract: Escherichia coli O157:H7 and Salmonella infections have been associated with consumption of a number of fruits and vegetables. Although the fate of E. coli O157:H7 and Salmonella on many of these products is well studied, little is known about their behavior on cut mango and papaya. Mangoes and papayas have been associated with four and two documented outbreaks of salmonellosis, respectively. The objective of this study was to evaluate the fate of E. coli O157:H7 and Salmonella on fresh (4°C, 12°C and 23°C) and frozen (−20°C) cut mangoes and papayas. Cut mangoes and papayas were spot inoculated with either a four-strain or five-strain cocktail of E. coli O157:H7 or Salmonella, respectively. Inoculated samples were air dried, placed in containers and stored at 4±2, 12±2, 23±2 and −20±2°C. Samples were enumerated following stomaching on nonselective and selective media at days 0, 1, 3, 5, 7, 10, 14, 21 and 28 (4±2 and 12±2°C); 0, 1, 3, 5 and 7 (23±2°C); and 0, 7, 14, 21, 28, 60, 90, 120, 150 and 180 (−20±2°C). Population levels (log CFU/g) of fruit were calculated. E. coli O157:H7 and Salmonella have the potential to grow on temperature-abused fresh cut mangoes and papayas held at 23°C. At 12°C, Salmonella populations can grow on cut mangoes and papayas, however E. coli O157:H7 populations only grew on papayas. E. coli O157:H7 and Salmonella survived for 28days, at 4°C, on refrigerated mangoes and papayas. E. coli O157:H7 and Salmonella can survive on frozen cut mangoes and papayas for at least 180days. Fresh and frozen cut mangoes and papayas are potential vectors for E. coli O157:H7 and Salmonella transmission. [Copyright &y& Elsevier]

Pineapples have been associated with outbreaks of Escherichia coli and Salmonella. Little is known about the behavior of E. coli O157:H7 and Salmonella on cut pineapple. The objectives of this study were to evaluate the fate of E. coli O157:H7 and Salmonella on fresh and frozen cut pineapples and the influence of acid adaptation on Salmonella survival on fresh cut pineapple at ambient storage (23°C). Cut pineapples were spot inoculated with a four-strain cocktail of E. coli O157:H7 or a five-strain cocktail of Salmonella. Inoculated samples were air dried, placed in containers, and stored at 4, 12, 23, and -20°C. Samples were stomached and then enumerated on nonselective and selective media at days 0, 1, 3, 5, 7, 10, 14, 21, and 28 (4 and 12°C); 0, 1, 3, 5, and 7 (23°C); and 0, 7, 14, 21, 28, 60, 90, 120, 150, and 180 (-20°C). E. coli O157:H7 and Salmonella inoculated onto pineapple did not grow but survived for the shelf life at each temperature, with improved survival at lower temperatures. E. coli O157:H7 and Salmonella can survive on frozen cut pineapples for at least 180 days. Acid adaptation of Salmonella did not allow growth and did not increase survival. Fresh and frozen cut pineapples are potential vectors for E. coli O157:H7 and Salmonella transmission and preventive procedures should be implemented during production and postharvest processing. [ABSTRACT FROM AUTHOR]

Abstract Strategies to mitigate antibiotic-resistant bacteria (ARB), including human pathogens, on raw vegetables are needed to reduce incidence of resistant infections. The objective of this research was to determine the effectiveness of standard post-harvest interventions, sanitizer washing and cold storage, to reduce ARB, including antibiotic resistant strains of the human pathogen E. coli O15:H7 and a common spoilage bacterium Pseudomonas, on raw carrots. To provide a background inoculum representing potential pre-harvest carryover of ARB, carrots were dip-inoculated in dairy cow manure compost slurry and further inoculated with known ARB. Inoculated carrots were washed with one of three treatments: sodium hypochlorite (50 ppm free chlorine), peroxyacetic acid (40 ppm peroxyacetic acid; 11.2% hydrogen peroxide), tap water (no sanitizer), or no washing (control). Washed carrots were air dried, packaged and stored at 10 °C for 7d or 2 °C for up to 60 d. Enumeration was performed using total heterotrophic plate counts (HPC), HPCs on antibiotic-containing media ("ARBs"), E. coli O157:H7, and Pseudomonas sp. immediately after washing (0 d) and after 7 d of storage. In addition to the cultured bacteria, changes to the surficial carrot microbiota were profiled by sequencing bacterial 16S rRNA gene amplicons to determine the effect of sanitizer wash, storage temperature, and time of storage (0, 1, 7, 14 and 60 d). Storage temperature, addition of a sanitizer during wash, and duration of storage significantly affected the bacterial microbiota (Wilcoxon, p < 0.05). Inclusion of either sanitizer in the wash water significantly reduced the log CFU/g of E. coli O157:H7 and Pseudomona s sp., as well as HPCs enumerated on cefotaxime- (10 μg/ml), sulfamethoxazole- (100 μg/ml), or tetracycline (3 μg/ml) supplemented media compared to the unwashed control (ANOVA, p < 0.05). However, no significant reductions to bacteria resistant to vancomycin or clindamycin occurred after washing and storage. Members of the Proteobactetria, Firmicutes, Actinobacteria, Planctomycetes , and Acidobacteria comprised the bacterial carrot microbiota. The diversity of the carrot microbiota was significantly affected by the temperature of storage and by extended storage (60 d), when spoilage began to occur. There were no significant differences to the relative abundance of bacterial groups associated with the type of sanitizer used for washing. Results of this study indicate that inclusion of a sanitizer in wash water, followed by storage at 2 °C, might be an effective strategy to prevent re-growth of pathogenic E. coli O157:H7 and reduce levels of bacteria resistant to certain antibiotics on carrots. Highlights • Sanitizer washed carrots carried fewer antibiotic resistant bacteria. • Sanitizer reduces E. coli O157 on carrots, storage at 2 °C prevented regrowth. • Storage at 2 °C prevents growth of spiked antibiotic-resistant Pseudomonas sp. on carrots. • Storage at 10 °C was associated with growth of bacteria resistant to cefotaxime on carrots. • Storage temperature, not sanitizers, resulted in the most changes to carrot microbiota. [ABSTRACT FROM AUTHOR]

Abstract Fresh herbs are popular commodities that generally undergo minimal processing. Salmonella and Escherichia coli O157:H7 survival has been observed on herbs; however, little data exists on the survival of Listeria monocytogenes on herbs. The purpose of this study was to evaluate the survival of L. monocytogenes on the surface of basil, cilantro, dill, and parsley plants grown in a greenhouse. Greenhouse production continues to increase worldwide due to a year-round growing season and controllable conditions. Herb plants were grown in a greenhouse with average temperature of 21 ± 5 °C and relative humidity of 62 ± 10%. Each herb plant was inoculated with a five-strain nalidixic acid-resistant cocktail of L. monocytogenes. Samples were enumerated using standard methods at time-points: 0, 0.21, 1, 2, 3, 7, 14, 21, and 28 d. Population levels in log CFU/g of each herb plant were calculated. The initial inoculum was approximately 4–5 log CFU/g for each herb plant. Overall, L. monocytogenes populations did not grow on the studied herb plants; however, L. monocytogenes was able to survive on the surface of the studied herb plants for up to 28 d, except parsley plants, which fell below the limit of detection 7 d post-inoculation. L. monocytogenes populations demonstrated a similar biphasic survival curve on each of the four different herb plants. L. monocytogenes population decline was most evident within the day post-inoculation for all herb plants. Between 0 and 1 d, L. monocytogenes populations significantly decreased by 3.3, 2.4, 2.6, and 3.2 log CFU/g for basil, cilantro, dill, and parsley plants, respectively. Additionally, within that first 24 h, L. monocytogenes populations significantly decreased on the surface of all herb plants at 5 h post-inoculation (approximately 2.4, 1.6, 2.7, and 2.0 log CFU/g for basil, cilantro, dill, and parsley plants, respectively). No significant difference was observed in L. monocytogenes populations between each of the four herb plants after 7 d post-inoculation. Since L. monocytogenes exhibited survival on the herb plants studied, the adoption of pre-harvest best practices (e.g., sanitation, Good Agricultural Practices) is fundamental to limiting the introduction of contamination, especially in greenhouse environments. Highlights • Data generated can be used in risk assessments or predictive modeling efforts. • L. monocytogenes survived on the surface of herbs for at least 28 d, except parsley. • L. monocytogenes populations declined rapidly on the surface of herbs within 24 h. • L. monocytogenes survival may be reduced if greenhouses can minimize high humidity. [ABSTRACT FROM AUTHOR]

Background Food safety is a priority for all stakeholders associated with the food supply and consumption. Outbreaks and recalls caused by microbial pathogens are widely attributed to contaminated foods, and lead to considerable public health and economic burdens. Scope and approarch This review presented major current trends in food safety research, regulation and strategic development. Specifically we discussed about: (i) worldwide application of genomic data in foodborne pathogen surveillance and outbreak investigation; (ii) Geographic Information Systems (GIS) in food safety to prevent and predict pathogen contamination; (iii) modeling tools adapted from landscape ecology, network analysis and niche modeling to prevent foodborne diseases; and (iv) meta-analysis of food safety data to facilitate decision making. Key findings and conclusions While some of these technologies are receiving increasing recognition around the world (e.g., WGS), others are still at their infancy in regards to their application in food safety (e.g., meta-analysis). The establishment of relevant, valid and multi-dimensional databases is the key to effective application of many new trends in food safety described in this review. [ABSTRACT FROM AUTHOR]